Compact, wide-angle radiation-steering devices are valuable in fields such as information display, optical communications, and laser-steering. The electromagnetic radiation can be of any frequency, such as visible radiation or infrared. The embodiments discussed in this disclosure pertain to three-dimensional (3D) image display, particularly to view-sequential autostereoscopic three-dimensional display.
One class of methods for producing the perception of an “aerial” 3D image is known as multi-view autostereoscopic display. These methods typically create 3D imagery, visible to the unaided eye (i.e. they do not require the use of polarized glasses), created by projecting multiple depictions of the desired scene as rendered from a series of viewpoints, usually as rendered by a computer-graphic camera moving along a horizontal track.
3D displays have taken many forms, such as parallax panoramagrams which use lenticular display elements (“lenticules”) or parallax barriers to spatially demultiplex and steer light from an image surface to one or more viewing regions. Lenticules may be biconvex, or made of multiple surfaces, and may alternatively be long, thin lenses having a flat surface on one side and an opposing curved surface, forming a plano-convex lens. When viewed, the lenticule may provide a view angle-dependant striped or sliced portion of an image positioned behind each lenticule (i.e., the slice that is viewable is dependent upon the angle from which the viewer views the image).
Therefore, arrays of lenticules can be used to create a parallax effect wherein different views or slices of total images are apparent from different viewing angles. In this way, a 3D effect can be achieved if the components of a 3D image are successfully rendered as separate slices, presented at the image surface as spatially multiplexed views, and are viewed through a lenticular array in a parallax manner.
The lenticular array concept has been used to create “no 3D glasses required” or “autostereoscopic” displays. Typically, such displays use a sheet array of lenticular lenses to steer interdigitated left, intermediate and right eye views to a properly positioned observer.
Lenticular 3D displays techniques deserve their own category because they have earned a competitive place in the commercial market. However, the number of views they are capable of displaying is usually limited because they employ spatial-multiplexing, whereby the resolution of the display is sacrificed to include parallax information. The minimum pixel size is consequently a limiting factor in these displays.
Interactive electronic flat panel 3D displays have been developed based on these techniques.
For example, StereoGraphics Corporation (San Rafael, Calif.) sells the SynthaGram™ flat panel monitor series which is a lenticular-based 3D display. The SynthaGram series ranges from XGA (1024×768 pixel) to UXGA (3840×2400 pixel) monitors, and employs a custom fabricated diagonal lenticular screen which divides pixels into 9 different views. The monitor is driven by the DVI data output of a graphics card. The lenticular screen is designed to eliminate moire fringing, which can occur in lenticular flat panel screens, and divides pixels on the RGB level.
The drawback of existing lenticular 3D displays, and all spatially-multiplexed multi-view 3-D displays, is that by definition they trade off the projector's spatial resolution for the number of views displayed. The number of views is also limited by the shape of the lenticular elements and the pixel size. To date lenticular displays have produced at most 12 views. Furthermore, existing lenticular displays have typically been implemented using components that are relatively large or stationary, and do not support mobile operation.
A requirement common to view-sequential displays is beam steering, which can be performed by a rotating mirror, a translating transparent column on a black background in the system's Fourier plane, or other methods.
Several applications, such as mobile graphics visualization (i.e. quasi-holographic aerial imagery projected from a mobile phone or portable media device) and desktop 3-D visualization, require the 3-D display to be “thin.”
What is needed is a compact radiation steering device that is amenable to mobile operation (such as in a handheld device) that consumes and emits less power that prior art approaches. Preferably, the radiation steering device can be fabricated from low-cost components and is useful in tight spaces.